Work pursued with the support of this grant includes the following. First, carbon-13 nmr studies of human plasma lipoproteins are designed to reveal certain details of the structural organization of these complex aggregates and to provide information concerning the segmental and rotational motions of the constituent lipids. Second, carbon-13 nmr studies of the human plasma lipoproteins following trypsinization will provide information pertinent to the question of the dependence of structural organization and barriers to motions of individual classes of carbon atoms on the integrity of approtein structure. Third, mixtures of lipids in triolein will be studied by carbon-13 nmr in an effort to determine the thermodynamics of interaction of lecithin with cholesterol and cholesterol derivatives. Finally, the relationship between structure and the catalytic activity of melittin for hydrolysis of phospholipids will be probed through selected modification of the melittin molecule and determination of kinetic parameters.